1. Field of the Invention
The present invention relates generally to gas turbine blades and, more particularly, to hollow gas turbine blades formed by a casting operation that leaves core printout holes therein. Specifically, the invention relates to a method and apparatus for closing core printout holes in superalloy gas turbine blades.
2. Description of the Related Art
Turbine blades are employed in different regions of combustion gas turbine engines. As is known in the related art, such combustion gas turbine engines typically include a compressor section, a combustor section, and a turbine section. Air is drawn into the engine and compressed by the compressor section, with fuel being mixed into the compressed air and the fuel/air mixture being combusted in the combustor section. The hot combusted gases then flow past the turbine section and thereafter exit the engine.
The turbine section of the engine typically includes a plurality of blades that are mounted on a common rotating shaft. The turbine section each additionally includes one or more stators having a plurality of non-moving vanes or blades that cooperate with the moving blades mounted on the rotating shaft to derive mechanical power from high velocity gases.
Since the blades of the turbine section, both moveable and stationary, operate in a high temperature environment, such turbine blades are typically formed in a casting operation to include a hollow cavity. The cavity receives cooling air during operation of the combustion engine to provide a cooling effect to the blades and to control the operating temperature thereof. The hollow cavity is cast into each turbine blade by providing a core within the blade mold. The core is retained within the mold by one or more ceramic rods that extend from the core to the inner surface of the mold itself for retaining the core in a given position within the mold. A molten alloy is then poured into the mold with the core disposed therein, whereby the core prevents the flow of the molten alloy within desired regions of the mold and ultimately results in a hollow region or cavity within the finished turbine blade that can receive the beneficially cooling air therein.
During the casting operation, however, the ceramic rods that retain the core in the desired position within the mold likewise themselves prevent the flow of the molten alloy such that the finished turbine blade additionally and undesirably includes one or more core printout holes resulting from the ceramic rods. Such core printout holes must be sealed prior to use of the turbine blade, otherwise the cooling air introduced into the hollow region or cavity of the turbine blade will undesirably flow out of the printout hole without providing the needed beneficial cooling effect to the turbine blade.
Previous methods and apparatuses employed to seal such core printout holes have met with only limited success due to the difficulty of attaching or bonding a seal strongly enough to the turbine blade to withstand the typical operating environment. As is known in the relative art, such blades typically are manufactured out of a xe2x80x9csuperalloyxe2x80x9d that typically is of a nickel base that is alloyed with other materials such as aluminum, titanium, chromium, and other materials in various combination and proportions, although numerous other alloys can be used for the manufacture of turbine blades. Such superalloys typically include nickel aluminide intermetallic crystals that are extremely brittle and are precipitated within a solid solution that makes up the turbine blade. Welding of such nickel-based superalloy materials is extremely difficult and often results in cracking and microfissuring due to strain age and liquation cracking. A need thus exists for a method of sealing core printout holes whereby a sealing member is sufficiently strongly and sealingly mounted on the turbine blade while avoiding the necessity of applying a weld directly to the superalloy turbine blade.
In accordance with the foregoing, an aspect of the present invention is to provide a sealing member that seals a core printout hole in a turbine blade of a combustion gas turbine engine. The sealing member includes a plug member and first and second leg members. The plug member is formed generally in a top hat configuration and is disposed in a cavity formed in the blade, the plug member being retained in the desired sealing position by the leg members. The plug member broadly serves the purpose of sealing the hole that is in communication with the cavity. The plug member includes a substantially planar plate that is disposed adjacent the internal first surface of a wall of the turbine blade and a retention member that is received in the hole. The first and second leg members are fixedly mounted, such as by welding, on the plug member and are at least partially disposed adjacent and overlap a second opposite and external surface of the wall.
Another aspect of the present invention is to provide a sealing member for sealing a hole in a wall of a blade of a combustion gas turbine engine, the blade being formed with a cavity, the hole being in communication with the cavity, the general nature of which can be stated as including a plug member having a plate and a retention member, the plate being structured to be disposed at least partially within the cavity and at least partially adjacent a first surface of the wall, the retention member extending from the plate and being structured to be disposed at least partially within the hole, and a first leg member attachable to the plug member, the first leg member being structured to at least partially overlap a second surface of the wall, the second surface being opposite the first surface.
Still another aspect of the present invention is to provide a gas turbine engine, the general nature of which can be stated as including a compressor section, a combustor section, and a turbine section, the turbine section including at least a first blade, the at least first blade having a wall and being formed with a cavity and a hole, the hole extending through the wall and being in communication with the cavity, a sealing member being mounted on the at least first blade, the sealing member including a plug member and a first leg member, the plug member including a plate and a retention member, the plate being disposed at least partially within the cavity and at least partially adjacent a first surface of the wall, the retention member extending from the plate and being disposed at least partially within the hole, and the first leg member being attached to the plug member, the first leg member at least partially overlapping a second surface of the wall, the second surface being opposite the first surface.
Yet another aspect of the present invention is to provide a method of sealing a hole in a wall of a blade of a combustion gas turbine engine, the blade being formed with a cavity, the hole being in communication with the cavity, the general nature of which can be stated as including the steps of receiving a plug member in the cavity, the plug member having a plate and a retention member, positioning the plug member such that the plate is disposed at least partially within the cavity and at least partially adjacent a first surface of the wall, and such that the retention member is at least partially received in the hole, and attaching a first leg member to the plug member such that the first leg member at least partially overlaps a second surface of the wall, the second surface being opposite the first surface.